New Callbacks() object

The jQuery.Callbacks() object returns a multi-purpose object used to manage callback lists. In essence, it’s a generalized way to queue and trigger a series of handlers. It’s an advanced feature — in most situations, the higher-level jQuery.Deferred object will be preferable.

Miscellaneous Improvements and Bug Fixes

The following issues have been addressed:

Delegate event performance has doubled in 1.7. The jQuery team identified that delegation had become increasingly important in application frameworks and made further optimizations to the core code.

Toggling animations including slideToggle() and fadeToggle() now work correctly following a termination of queued effects using stop().

The is() method now correctly filters positional selectors such as :first, :last and :even against the document — not the jQuery object passed to is().

Documentation Updates

For further details of all the new features, refer to the 1.7 documentation page. All new features are tagged with “New in 1.7”.

Should You Upgrade?

That’s the million dollar question. The jQuery team work hard to minimize compatibility issues and version 1.7 is unlikely to break your code. That said, if you’re particularly risk-averse, delay updating for a week or two. Minor bugs are normally found, fixed and released quickly.

Craig is a freelance UK web consultant who built his first page for IE2.0 in 1995. Since that time he's been advocating standards, accessibility, and best-practice HTML5 techniques. He's written more than 1,000 articles for SitePoint and you can find him @craigbuckler